1. Field of the Invention
The invention relates to the elevator art. More particularly, the invention relates to an elevator system which is particularly conducive to retrofitability in structures without elevator pits as well as new construction where a pit is not desired or permitted.
2. Prior Art
In the elevator art it has been conventional for a very long period of time to build an elevator hoistway, i.e. the shaft in which an elevator car is moved upwardly and downwardly, with a pit. A pit is a continuation of the hoistway downwardly below the intended lowest level at which the elevator car will have duty. The lowest level may be a first floor or a basement, etc. Typically, a pit is about 4-5 feet in depth below the lowest elevator car level and thus requires a substantial amount of excavation of material at not insignificant cost. Moreover, the deeper a pit is dug the more likely it becomes that the water table in the area will be reached which further complicates matters. Where an elevator system is a retrofit in an existing structure, the excavating of a pit is complicated further and further increases expense. Additionally, the pit takes up space that could be otherwise employed. The latter interpretation occurs where an elevator stops a level above a basement and the pit is located in the basement. Digging is thus not specifically required for the pit itself but a portion of the basement is lost and the elevator car, in a conventional system, could not be lowered to the basement level.
A pit is conventionally required for elevator systems in order to house the over limit car buffer and pit sheaves, and to provide clearance for the elevator car entrance toe guard which can be up to two meters in length and is rigid. The toe guard therefore requires in such a case at least two meters of clearance and preferably more to avoid bumping the bottom of the shaft when the elevator is at its lowest point. This could occur if insufficient space were left in the pit to receive the toe guard in the event the car continued too far downwardly in the hoistway (an over limit condition).
The foregoing limitations have been consistent drawbacks of the elevator art. In an era of ever increasing cost of space and construction, the art is in need of pitless elevator systems for both new construction and retrofit applications in existing structures.